There are lots of researches working on a three-dimensional image and an image playback technology, which technology currently gathers huge interesting throughout the world.
The image-related technology advances more and more, so the images become highly integral.
Thanks to that, the three-dimensional images becomes realistic and look more natural as compared to a two-dimensional image, so needs for such three-dimensional images increase day by day.
The three-dimensional image playback technology is directed to a technology which enables an observer to enjoy a three-dimensional image, not a plane image, in more three-dimensional and actual-looking ways.
As a method for playing-back three-dimensional images, there are a stereoscopy method, a holography method and an integral imaging method, which advance over time.
The integral imaging method was developed in 1908 by Lippmann. Afterward, the integral imaging method is advancing to the next generation three-dimensional playback technology.
As a prior art of the above mentioned integral imaging method, there is a method for compressing element images with the aid of a region division technology using an element image compression device disclosed in Korean patent registration No. 0891160, which method comprises (a) obtaining an element image with a different parallax from a three-dimensional object through a lens array, (b) dividing into a similar region with a plurality of similar images depending on the similarity of the obtained element images; (c) rearranging the images included in each similar region to an one-dimensional element image arrangement, and (d) compressing the rearranged and generated one-dimensional element image arrangement.
As another example of the prior art, there is a method for recovering an integral image using an element image picked up through a lens array disclosed in Korean patent registration No. 0942271, which method comprises generating a recovery image by expanding the element image to a previously set size and combining the pixels positioned on the same coordinate of each expanded element image; measuring the blur matrix value of each recovery image; selecting as a focus image the recovery image corresponding to the inflection point of the blur matrix value based on a focus distance; generating an erosion image through an erosion computation, which computation means to subtract each pixel value of a corresponding erosion mask from each pixel value of the focus image; and mapping the erosion onto the recovery image.
FIG. 1 is a view illustrating a basic principle of the integral imaging method.
The principle of playing back a three-dimensional object 110 as a three-dimensional image 210 consists of an image acquisition step 100 for obtaining an element image 130 by letting a three-dimensional object 110 go through a lenslet 120, and an image playback step 200 for playing back the element image 100 obtained in the image acquisition step 100 as a three-dimensional image 210 in a space through the lenslet 220.
As shown in FIG. 1, the integral image technology consists of an image acquisition step 100 and an image playback step 200.
The image acquisition step 100 comprises a two-dimension detection unit like an image sensor and a lenslet 120. The three-dimensional object 110 is disposed in front of the lenslet 120.
Various image information of the three-dimensional object 110 pass through the lenslet 120 and are stored in the two-dimension detection unit.
At this time, the stored images are used for the sake of the playback of the three-dimensional image 210 as an element image 130.
The image playback step 200 of the integral image technology is performed in the way reverse to the image acquisition step 100 and is implemented with the image playback device like a LCD and the lenslet 220.
The element image 230 obtained in the image acquisition step 200 is displayed in the image playback device, and the image information of the element image 230 passes through the lenslet 220 and is played back as a three-dimensional image 210 in a space.
The element image 130 of the image acquisition step 100 and the element image 230 of the image playback step 200 are actually same, except that the element image 230 of the image playback step 200 is used for the sake of the playback of the three-dimensional image as the element image 120 obtained in the image acquisition step 100 is stored in the two-dimension unit. They are given different reference numerals in order to classify the image acquisition step 100 and the image playback step 200.
The direct imaging method is advantageous in that like the holography method, the full parallax and the continuous view timing can be provided.
The major features of the direct imaging method lie in that glasses or other tools are not necessary when observing three-dimensional images while providing continuous vertical and horizontal parallaxes within a certain viewing angle, not timing.
In addition, the direct imaging method is featured in that the full colors real-time image playbacks are possible and it is well compatible with the conventional flat image device.
FIG. 2 is a view illustrating a depth-based direct imaging method, and FIG. 3 is a view illustrating a resolution-based direct imaging method.
The above mentioned direct imaging method may be classified into two kinds depending on a distance “g” between the lenslet 220 and the element image display device.
In other words, it can be classified into two occasions, of which one occasion is when the distance “g” is the same as the focal distance “f” of the basic lens of the lenslet 220 and the other occasion is when it is not same.
When “g”=“f”, as shown in FIG. 2, one pixel of the element image 230 becomes parallel beam through the lens for thereby producing a direct beam.
The above mentioned occasion is called a depth-based direct imaging method, by which it is possible to make maximum the region of the depth indicating a three-dimensional image; however it is disadvantageous in that the resolution of the three-dimensional image 210 is low.
When “g” is not same as “f”, it is called the resolution-based direct imaging method, in which one pixel of the element image 230 becomes a convergence beam through the lens for thereby generating a direct beam. In this case, the resolution of the three-dimensional image 210 can be increased; however the depth region decreases.